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    SubjectRe: Header files and the kernel ABI
    On Jul 25, 2002  00:07 -0700, H. Peter Anvin wrote:
    > Andreas Dilger wrote:
    > >The kernel side would be something like <linux/scsi.h> includes
    > ><linux/abi/scsi.h> or whatever, but in the future this can be included
    > >directly as needed throughout the kernel. The existing kernel
    > ><linux/*.h> headers would also have extra kernel-specific data in them.
    > >
    > >The same could be done with the user-space headers, but I think that
    > >is missing the point that the linux/abi/*.h headers should define _all_
    > >of the abi, so we may as well just use that directly.
    >
    > Except now the paths are gratuitously different between kernel
    > programming and non-kernel programming, and we create a much harder
    > migration problem. I'd rather leave the linux/* namespace to the
    > user-space libc to do whatever backwards compatibility cruft they may
    > consider necessary, for example, <linux/io.h> might #include <sys/io.h>
    > since some user space apps bogusly included the former name. Leaving
    > that namespace available for backwards compatibility hacks avoids those
    > kinds of problems.

    OK, but essentially then <linux/io.h> will be mostly a hollow shell
    which includes <linux/abi/io.h> and maybe a couple other files
    (e.g. <linux/abi/types.h> or similar). If so, then great.

    That brings up the question - how do you tie a particular
    <linux/abi/*.h> to a particular kernel? Should there be a bunch of
    directories <linux/abi-2.4/*.h> and/or <linux/abi-2.4.12/*.h> and/or
    <linux/abi-`uname -r`/*.h> or what? While there are efforts to keep
    the ABI constant for major stable releases, this is not always true,
    so abi-2.4 will certainly not be enough. Maybe linux/abi is a symlink
    to the abi directory of currently running kernel?

    Cheers, Andreas
    --
    Andreas Dilger
    http://www-mddsp.enel.ucalgary.ca/People/adilger/
    http://sourceforge.net/projects/ext2resize/

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